Method for preparing chromium-containing sludge ceramsite

Abstract

The invention discloses a method for preparing chromium-containing sludge ceramsite. The method comprises the following steps of: performing wet grinding on chromium sludge to be 120 meshes; drying municipal sludge, decomposed rock, silt or kaolin and performing dry grinding together with a reducing agent to be 100 meshes; uniformly mixing and pressing into strip-shaped particles with diameter of 10 mm and length of 20 mm; and balling, drying and then feeding into a rotary kiln to calcine at the high temperature of 1,230-1,330 DEG C for 45 minutes to obtain the chromium-containing sludge ceramsite. The method has the characteristics of capability of treating chromium-containing sludge produced by leather production, complete and reliable detoxication, simple process, large sludge consumption, capability of simultaneously treating most of heavy metal pollutants and low production cost, and has the advantages of feasible technology and minimum cost compared with various methods for treating heavy metal in China at present. Inspection shows that a finished product meets the control index requirement of being used as a road bed material, concrete aggregate and light brick filler and being used for producing cement.

Description

technical field [0001] The invention belongs to the field of material preparation, and in particular relates to a method for preparing chromium-containing sludge ceramsite. Background technique [0002] A certain amount of chrome tanning agent is used in the leather production and processing process. With the washing process, excess chromium-containing compounds flow into the wastewater, and chromium hydroxide precipitates are formed by adding alkali, and chromium-containing sludge is formed after pressure filtration. Chromium salt is an important chemical product in the tanning industry. Every standard piece of cow hide produces about 1Kg of chromium-containing sludge, and the total chromium content of chromium-containing sludge is about 0.6-1.0%, of which Cr 6+ Accounted for 40%, Cr 6+ Toxic, it can cause chromium sores, nasal septum erosion, blood chromium, lung cancer and other diseases. The lethal dose for humans is 5-8 grams. In 2012, my country's leather output (e...

AI Technical Summary

Problems solved by technology

Chromium-containing sludge is toxic and dangerous waste. If there is no reliable disposal and detoxification plan, the highly toxic Cr6+ in the mud pile will enter the soil and groundwater with rainwater, and it will pollute a lot Land and groundwater seriously restrict the development of the leather industry

Since the 1970s, the whole country has attached great importance to it and arranged more than ten projects. However, an effective, economical and practical treatment method has not been found so far. The treatment of chromium-containing sludge is still a very serious problem.

Dry detoxification mainly has the following types and existing technical problems: (1) According to the company's test, the original phase structure in the chromium-containing sludge cannot be destroyed when the temperature is lower than 1150°C, and new minerals cannot be formed. Cr 3+ reduced by 6+ is in an unstable or metastable state

(2) Use medium temperature and add substances such as SiO2 that are acidic at 1150°C-1300°C to achieve a local melting state, which can completely destroy the phase structure of chromium mud and form new minerals, which can effectively Treatment of chrome mud, but stoneware products, bricks and other burnt earth products have shape, size and appearance requirements, so it is not suitable for treatment of chrome mud, only concrete aggregate does not have the above limitations

(3) There are great hidden dangers in the treatment of chromium slag by medium and high temperature cement mineralizers

The use of chromium mud to replace part of the lime for sinter ironmaking has recently made some progress, but the process adjustment caused by this, the dust removal level of each dust point will be improved, the secondary pollution will be prevented, and the invalid components in the chrome mud will be generated. a certain potential cost

[0006] Due to the presence of insoluble calcium chromate solid solution in chromium mud, the existing structure of chrome mud must be destroyed in order to detoxify reliably. Among the chrome slime treatment methods, the most reliable and thorough detoxification method is the method of melting chrome slime into a liquid at a temperature above 1500°C. This method consumes a lot of energy, refractory materials are very expensive, and the cost or potential cost is very high. , the proportion of chromium mud added is low, the amount of slag eaten is small, the transportation distance is long, and it is difficult to prevent secondary pollution, which has certain limitations

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